Projection system



May 2, 1967 E. F. PERLOWSKI, JR 3,317,664

PROJECTION SYSTEM Filed Aug. 26, 1964 SCREEN ELECTRON GUN INVENTOR EDWARD F. PERLOWSKLJR.

HIS ATTORNEY.

United States Patent York Filed Aug. 26, 1964, Ser. No. 392,107 12 Claims. (Cl. 1787.5)

This invention relates to projection systems of the electronic type. More particularly, it relates to such projection systems having a container with a conducting interior and a deformable medium in the container that decreases in resistivity with decreases in thickness in the presence of an electrical charge on the surface of the medium, the medium being the polymeric reaction product of benzyl chloride and naphthalene.

There is described in US. Patent 2,943,147, June 28, 1960, assigned to the same assignee as the present invention, a projection system of the above type employing a deformable medium having a high resistivity which is responsive to a velocity modulated electron beam. Generally speaking, this projection system, which is illustrated in FIG. 1 of the drawing, comprises an evacuated glass envelope containing an electron gun .11 for producing an electron beam 13 deflecting the beam in a rectangular raster over the surface of a light transmitting deformable medium 15 which is within a portion 17 of the transparent container. An enlarged view of this portion of the assembly is shown in FIG. 2. The beam 13 is preferably velocity-modulated by a television signal applied to the deflection means (not shown) inthe electron gun 11. Deformable medium 15 has a central portion 19 of decreased thickness which is coincident with the raster area of beam 13 produced by electrons from beam 13 which are attracted to a conducting coating 21 on the inner surface of the container portion 17. These same electrons also produce deformations in the surface of the deformable medium 15 and the amplitudes of these deformations are a function of the number of electrons deposited by the beam .13 at the various points on the surface of medium 15. Thus, the amplitudes of these deformations are a function of the modulated electron beam 13.

The deformations on the surface of medium 15 are utilized to ditfract light from a source 23 in an optical system including a lens 24 which projects an image of light source 23 on the surface of medium 15 through a bar and slit system 25. Another lens 29 images the slits of system on the bars of another bar and slit system 31 if there are no deformations on the surface of deformable medium 15. However, any deformations on such surface diifract the transient light so that it passes through the slits in the system 31 with an intensity that corresponds to the amplitudes of the deformations and hence the amplitudes of the applied modulating signal such as a television signal. The light passing through system 29 is imaged by a projection lens 33 on screen 35 by means of mirror 37.

If a conventional deformable medium is utilized at 15 in the illustrated system, the average charge density produces a force on the medium 15 that overcomes the surface tension from the excess medium outside the raster area and decreases the portion 19 of medium 15 to zero thickness. Under such conditions, no deformations can be formed and the system becomes inoperative until the medium is replaced. The above patent teaches that if the medium has the property of decreasing in resistivity with decreasing thickness, portion 19 does not decrease to zero thickness under the pressure of the charges but maintains a thickness which is a function of the magnitude of charge density on the surface of the medium 15. With decrease in resistivity, the time constant is decreased for the passage of leakage current from the surface of deformable medium 15 to the conducting coating beneath it. This results in an increase in leakage current, decreasing the charge density on the surface of the medium 15 and somewhat relieving the pressure. Eventually, an equilibrium condition is reached in which the pressure from the charges on the surface of the medium equals the pressure from the surface tension on the excess medium surrounding the raster at which the thickness at this equilibruim condition is maintained. The charge density on the surface of the medium never decreases to zero because of such leakage because it is continually being replaced by electrons from beam 13.

The deformable compositions described in the aforesaid Patent, US. 2,943,147, as suitable for the medium are required to be transparent, be capable of withstanding electron bombardment without significant decomposition, have a viscosity at the operating temperature (between about 25 C. and 150 C.) of approximately 100 to 50,000 centistokes, and the deformable composition must not decompose the conducting coating. The medium must also have a volume resistivity that varies within the range of approximately 10 to 10 ohms-cm, with the average resistivity at the stable thickness being approximately 10 ohms-cm.

Among the deformable media or fluids described in the above patent are, for instance, beeswax, methyl silicone fluids, methyl silicone fluids containing up to 5% of phenyl silicones, methylphenyl silicones containing an average of two methyl and phenyl groups per silicon atom in which the mole ratio of methyl groups to silicon atoms is greater than zero and less than 2, etc. However, it has been found that these deformable fluids are not as stable as one would desire because under the influence of an electron beam, the deformable medium or deformable fluid tends to increase in viscosity and with continued use of the projection system described above, the viscosity increases to a point where gel particles begin to form and ultimately the deformable medium gels. This means that the apparatus can no longer be used with that particular deformable medium.

It will be evident from the above that there is a continuing need for materials which can be used as medium 15 which are characterized by a desirably low rate of thickening under the radiation effects of electrons from beam 13. At the same time such materials should be characterized by good writing behavior under the action of electrons. They should have a good general working viscosity and small decrease in fluidity and use. They should i have a low vapor pressure and yield very little gas electronic bombardment. They should also be characterized by suitably high electrical resistivity and should be economical to use.

It is a primary object of this invention to provide materials which are possessed of such desirable qualities and a projection system of the above type which utilizes these qualities.

It has been found that the polymeric Friedel-Crafts reaction products of chloroalkylated aromatic materials, such as benzyl chloride with naphthalene, fit the above characteristics and provide a deformable medium which is possessed of long working life. Generally speaking the useful materials have a viscosity of at least centistokes (cs.) at 25 C. and have the other desirable qualities which have been found to be useful.

'Benzyl chloride is the preferred chloroalkylated material used herein. It will, of course, be appreciated that other halo-substituted benzyl materials of the above description can be used such as the iodoand bromo-substituted materials. However, the chloro-substituted materials are preferred from the point of View of cost and ready availability as well as from the point of view of easier processing. In addition to naphthalene, various hydrocarbon-substituted naphthalenes can also be used. For example, methyl naphthalene is very useful as are the aromatic-substituted materials and aralkyl-substituted naphthalene such as the benzyl-substituted material. Mixtures of the above materials are also useful.

Aluminum chloride is preferred as the catalyst material but other materials well known to those skilled in the art, including zinc chloride, ferric chloride, mercury zinc amalgam, mercury sodium amalgam, and boron trifiuoride, as well as various silicate materials, can be used. Generally speaking, any Lewis acid material or equivalent can be used.

Generally speaking, in forming the present materials, preferably from about 0.8 to 3 moles of chloro-methylated aromatic material, such as benzyl chloride, are used for each mole of aromatic hydrocarbon and most preferably at least about one mole of halogenated material for each mole of aromatic hydrocarbon. Broadly speaking, from about 0.1 to about 10 moles of chloromethylated material is used for each mole of naphthalene. The following examples illustrate the practice of the present invention, it being appreciated that they are not to be taken as limiting in any way.

EXAMPLE 1 There were added to a mixture of 256 grams (2 moles) naphthalene, 800 cc. cyclohexane and 2 grams aluminum chloride at 27 C. with mixing, 308 grams (2.44 moles) benzyl chloride over a onehour period, the reaction temperature being maintained at from about 27 C. to 33 C. Stirring was continued for an additional two and onehalf hours to insure completion of reaction, and during this time an additional two grams of aluminum chloride was added to increase the rate of reaction. At the end of the reaction period the mixture was neutralized with dilute (6N) hydrochloric acid, washed with hot potassium hydroxide solution, dried over anhydrous potassium carbonate and treated with activated charcoal and Celkate to improve the color and remove impurities. Celkate is a synthetic magnesium silicate material made by the Johns- Manville Corporation. Solvent and light ends were removed from the product to provide a 63 mole percent yield of material having a boiling point of from about 180 C. to 325 C. at 25 microns Hg. This material was further distilled to provide a out having a boiling point of 220 to 257 C. at 2 microns Hg. This latter material proved to be very suitable for use in connection with the present system. The viscosity of the product at 50 C. was 1000 centistokes and the vapor pressure was 8 10" torr at 50 C. The refractive index at 25 C. was 1.6577. The selected fraction was subjected to electron irradiation with a 1500 kv. resonant transformer at a current input of 200500 microamperes at a dose of 20 10 roentgens/ minute to a total dose of .1000 megaroentgens. The total number of molecules of gas absorbed per 100 electron volts was 0.025. This gas consisted mostly of hydrogen "which can be readily pumped from the system. The above number of molecules of gas absorbed is about one-third that obtained with a polybenzyl toluene material. The viscosity increaes under irradiation was 2.5 mm. per 800 mr. as compared to above 8.5 mm. per 800 mr. experienced for a typical polybenzyl toluene medium. The low gas value and small change in viscosity along with the other suitable characteristics of the medium, such as good transparency and a resistivity of about 6 l0 ohm-cm, at 50 C. showed conclusively the suitability of such compositions as a deformable medium in a projection system of the present type. When the medium was used in the system as described very clear images were obtained and the fluid was used over long periods of time with no evidence of degradation, gelation or other failure.

4 EXAMPLE 2 To 1280 grams (10 moles) of naphthalene and 1000 cc. of dry cyclohexane warmed to 35 C., there was added 10 grams of anhydrous aluminum chloride. To this stirred mixture, 1645 grams (13 moles) of benzyl chloride were added dropwise over a period of about two hours While maintaining a reaction temperature at 32i4 C. Stirring and warming to 45 C. was continued for 7 hours with the occasional addition of more aluminum chloride for a total of an additional 7 grams, the reaction being neutralized after this point with 300 cc. of dilute hydrochloric acid. The organic layer was washed with hot potassium hydroxide solution, dried over potassium carbonate, treated with Celkate and filtered. The cyelohexane solvent was then stripped out and the reaction product distilled to give the following cuts:

Boiling Range, Mol Cut N0. Identity C. (Vapor Percent Pressure Torr) Yield Unreaeted Naphthalene 40-103 (10) Beuzyl Naphthalene 204-222 (10). Dibenzyl Naphthalene. -145 (10- 5. Polyhenzyl Naphthalen 147-247 (10- Pot Residue 247 (10 12.7

A redistillation of the combined cuts 3, 4 and 5 gave a polybenzyl naphthalene with the following properties after stripping.

Refractive index=1.6584

Resistivity, ohm-cm.=4 l0 (50 C.)

Vapor pressure, torr=7 10- (50 C.)

Viscosity, cs.=1292 (50 C.)

The above redistilled material was admirably suited to the present purpose as a writing medium.

EXAMPLE 3 Purified benzyl naphthalene in the amount of 590 grams (2.7 moles) was diluted with about one liter of dry cyclohexane and cooled to 10 C. There were added to the above mixture with stirring 12 grams of anhydrous aluminum chloride. Benzyl chloride in the amount of 342 grams (2.7 moles) was added to the above dropwise over a period of about 3 hours at a temperature ranging from about 3 to 16 C., the mixture being stirred for an additional 2 hours to complete the reaction. The reaction mixture was then neutralized with 500 cc. of dilute hydrochloric acid and the organic layer washed with hot potassium hydroxide solution, dried over anhydrous potassium carbon-ate and treated with Celkate. After removal of the cyclohexane solvent, distillation gave cuts as follows:

Boiling Range, M01 Out No. Identity C. (Vapor Percent Pressure Torr) Yield 1 Monoand Dibenzyl Naph- 143-222 (10- 12110110. 2 Polybenzyl Naphthalene 205 270 (10- 42 3 Pot; Residue 270 (10- ea. 1

The polybenzyl naphthalene represented by cut 2 above upon further stripping and treating in the usual manner provided a useful writing medium for light valves of the type described herein.

EXAMPLE 4 with concentrated hydrochloric acid and hot potassium hydroxide solution and purified in activated charcoal and Celkate material as described above. After removal of solvents, the following distillation fractions were obtained:

The polybenzyl naphthalene of Fraction 3 above, when treated in the usual manner, provides a material useful as a writing medium for light valves of the type described.

There are provided by the present invention deformable media which, because of their desirable transparency, viscosity, resistance to decomposition under electron bombardment, good resistivity, low vapor pressure and compatibility with other elements of the projection system are well suited for the use described. It will be realized that obvious modifications may be made without departing from the scope and spirit of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A projection system comprising a container having a conductnig interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of from about 0.1 to moles of halogenated, alkylated aromatic and one mole of a material selected from the group consisting of naphthalene, methyl-substituted naphthalene, aralkyl-substituted naphthalene, aromaticsubstituted naphthalene and mixtures thereof, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating With said conducting interior to subject the medium to a deforming force to produce deformations in the surf-ace of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

2. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of from about 0.8 to 3 moles of halogenated, alkylated aromatic and one mole of a material selected from the group consisting of naphthalene, methyl-substituted naphthalene, aralkyl-substituted naphthalene, aromatic-substituted naphthalene and mixtures thereof, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

3. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of at least one mole of halogenated, alkylated aromatic and one mole of a material selected from the group consisting of naphthalene, methyl-substituted naphthalene, ar-alkyl-substituted naphthalene, aromatic-substituted naphthalene and mixtures thereof, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

4. A projecting system comprising a container having a conducting interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of from about 0.1 to 10 moles of benzyl chloride and one mole of a material selected from the group consisting of naphthalene, methyl-substituted naphthalene, aralkyl-substituted naphthalene, aromatic-substituted naphthalene and mixtures thereof, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating With said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

5. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of from about 0.1 to 10 moles of benzyl chloride and one more of methyl-substituted naphthalene, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

6. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of from about 0.1 to 10 moles of benzyl chloride and one mole of aralkyl-substituted naphthalene, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium and a light and optical system for projecting lightas a function of the deformations in the surface of said medium.

7. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of from about 0.1 to 10 moles of benzyl chloride and one mole of aromatic-substituted naphthalene, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

8. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of from about 0.1 to 10 moles of benzyl chloride and naphthalene, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

9. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of from about 0.8 to 3 moles of benzyl chloride and one mole of naphthalene, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

10. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of at least one mole of benzyl chloride and one mole of naphthalene, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperat' ing with said conducting interior to subject the medium to a deforming force to produce deformations in the surf-ace of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

11. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the FriedelCrafts reaction product of lbenzyl chloride and naphthalene, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

12. A projection system comprising a container having a conducting interior, a deformable medium in said container comprising the Friedel-Crafts reaction product of benzyl chloride and benzyl naphthalene, electron beam means for producing an electrical charge on the surface of said deformable medium as a function of an applied electrical signal and cooperating with said conducting interior to subject the medium to a deforming force to produce deformations in the surface of said medium and a light and optical system for projecting light as a function of the deformations in the surface of said medium.

No references cited.

DAVID G. REDINBAUGH, Primary Examiner.

J. A. ORSINO, Assistant Examiner. 

11. A PROJECTION SYSTEM COMPRISING A CONTAINER HAVING A CONDUCTING INTERIOR, A DEFORMABLE MEDIUM IN SAID CONTAINER COMPRISING THE FRIEDEL-CRAFTS REACTION PRODUCT OF BENZYL CHLORIDE AND NAPHTHALENE, ELECTRON BEAM MEANS FOR PRODUCING AN ELECTRICAL CHARGE ON THE SURFACE OF SAID DEFORMABLE MEDIUM AS A FUNCTION OF AN APPLIED ELECTRICAL SIGNAL AND COOPERATING WITH SAID CONDUCTING INTERIOR TO SUBJECT THE MEDIUM TO A DEFORMING FORCE TO PRODUCE DEFORMATIONS IN THE SURFACE OF SAID MEDIUM AND A LIGHT AND OPTICAL SYSTEM FOR PROJECTING LIGHT AS A FUNCTION OF THE DEFORMATIONS IN THE SURFACE OF SAID MEDIUM. 